I am happy to receive my C5 white dragon, which is my first spirit. When I did the dragon invocation from CH, the vessel actually shake quite hard.(like someone knocked from inside the vessel) But this only happened on my first invocation, after that I did the invocation a few times but there was no knocking anymore. There is pulsing too. It feels like he vessel has a heartbeat on its own. Thats all for now.

Well, strictly speaking, the invocation doesn't even need to be done in the first place so since you had a reaction the first time you did it then it doesn't surprise me nothing happened later - your dragon has already said "HI" - great beginnings